Manila filed a case at a UN tribunal in March challenging Chinese claims to most of the strategic sea. Aquino said he would discuss the case's regional implications with fellow Association of Southeast Asian Nations (ASEAN) leaders meeting in Myanmar.
Even though not all ASEAN members are involved in maritime territorial disputes with China, Aquino said the issue concerned the security of the region as a whole.
Myanmar is hosting the two-day meeting amid a flare-up of high-seas tensions between ASEAN members Vietnam and the Philippines and regional superpower China, also one of their main economic partners.
China claims most of the South China Sea, including waters and rocks close to the shores of its neighbours, and the Philippines and Vietnam have both accused Beijing of increasingly aggressive moves to assert its claims.
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The sea is crisscrossed by fishing and shipping lanes and is thought to contain huge oil and gas reserves.
Hanoi said this week that Chinese ships that had surrounded a Chinese deep-water oil rig in waters claimed by Vietnam had used water cannon against, as well as rammed, Vietnamese patrol vessels there.
Meanwhile, Manila said it arrested 11 crew members of a Chinese-flagged fishing boat Tuesday for poaching hundreds of protected marine turtles in waters that are part of the Philippines' exclusive economic zone.
China has rejected arbitration in the Philippines' UN case, preferring to settle the issue through bilateral negotiations while insisting its sovereignty over these areas was "indisputable".